248 ASSINNIBOINE AND SASKATCHEWAN EXPEDITION. 



shows stratification, and is evidently lacustrine. The 

 unstratified clay contains a large per centage of magnesia 

 derived from the underlying rocks. 



At Lane's Post on the Assinniboine, the quaternary 

 lacustrine deposit, eight feet below the surface, pre- 

 sents the appearance of irregularly stratified bands 

 of extremely fine material deposited in quiet waters. 

 Upon close examination the bands are found to consist 

 of a series, in which light ash-coloured and dark brown 

 layers alternate, about J to y 1 ^ of an inch in thickness. 

 In the light-coloured bands minute crystals of sulphate 

 of magnesia and common salt are common. The clay 

 is characterized by its extreme fineness, the marked 

 absence of silicious particles in the form of sand, and the 

 presence of carbonates of lime and magnesia in variable 

 quantities. In certain localities carbonate of lime exists 

 in proportions sufficient to constitute a marl. 



The following section is exposed at Lane's Post : — 



Feet. 



Vegetable prairie mould 1 



Unstratified alluvial clay ....... 5 



Stratified dark-coloured clay with liglit ash-coloured bands 12 



Total 18 



The subsoil on Eed Eiver, near the middle settlement, 

 four feet below the surface, is much darker coloured, 

 not so distinctly stratified, and contains abundance of 

 mica in very fine brilliant plates. The particles of the 

 subsoil on either river are extremely minute, and difficult 

 to separate by washing. 



The drift on the Blue Hills of the Souris is Chiefly of 

 local origin, and consists almost exclusively of the shales 

 which form the outcrop of the Cretaceous rocks whose 

 limit is defined by the Pembina Mountain. Its age is 



